Isoprenoids - Online Tutor, Practice Problems & Exam Prep

Isoprenoids are lipids formed from isoprene units, specifically 2-methyl-1,3-butadiene, a 5-carbon molecule. They are categorized into three major classes: terpenes and terpenoids, steroids, and lipid vitamins. Terpenes are linear isoprenoids, while terpenoids are more complex, often cyclic, and modified versions of terpenes. The number of isoprene units in these compounds can be determined by counting the methyl group branch points, rather than double bonds, which may not accurately reflect the structure. Understanding these classifications is essential for studying lipid functions and interactions in biological systems.

Isoprenoids

So now that we've explored all of our fatty acid based lipids, in this video we're finally going to transition and talk about the isoprenoids. Now before we get started, let's first revisit our lipid map just to make sure we're all on the same page. And we know that up until this point in our course, we've been exploring the left branch here and all of our fatty acid based lipids. And so in our previous lesson videos, we talked about all of these fatty acid based lipids that show up in our original lipid map. But here what we've done is we've gone ahead and condensed all of those down to just showing the fatty acid right here. And now that we've finished talking about our fatty acid Basal Lipids, we're finally going to explore this right branch and talk about the isoprenes and the isoprenoids. And so the isoprenoids, again, are their own branch of lipids here, and really, these are just lipids that are constructed from 2 or more units with the same carbon skeleton of a molecule called isoprene. And so again, isoprene is just a molecule and its IUPAC name or its scientific name is really just 2-methyl-1,3-butadiene. But really this is just a 5 carbon molecule, and it's this 5 carbon molecule that you see right here. What you might recall is the same exact molecule we use to symbolize all of our isoprenoids in our previous versions of our lipid map. And so, you can also see that this isoprene molecule is shown right down here. And so if we were to go ahead and number the main chain, carbon atoms here, you would see that there are a total of 4 carbon atoms in our main chain, which is what the buta prefix is referring to. The di is referring to 2, the ene is referring to double bonds. So notice that there are 2 double bonds, and of course, the 1 and the 3 are referring to the positions of those double bonds appearing at, carbon 1 and carbon 3. And then of course, the 2-methyl is referring to this methyl group here branching off of carbon number 2. But again, the main point here is that this is just a 5 carbon molecule and by taking multiple of these isoprene molecules and combining them together, we can build our isoprenoids. And really there are 3 major classes of isoprenoids that you guys should know moving forward and we have those numbered 1, 2, and 3 right here.

And so the first class of isoprenoid that you guys should know are the terpenes and the terpenoids. The second class are the steroids. And the third class are the lipid vitamins. And so if you take a look at our lipid map down below, notice that we're showing you the isoprenes here and again this is this molecule right here. Now if you take multiple of these isoprenes and link them together you can start to build our isoprenoids and there are 3 major classes of these isoprenoids, the terpenes and terpenoids, the steroids, and the lipid vitamins. And so as we move forward in our course, we're going to talk about each of these three different classes of isoprenoids, in their own videos. But for now, this here concludes our introduction to the isoprenoids and I'll see you guys in our next video.

Isoprenoids

In this video, we're going to begin our lesson on our first class of isoprenoids, which are the terpenes and terpenoids. Now, terpenes are simple linear isoprenoids with structures that more clearly reveal that they're actually derived from isoprene units. And so if we take a look at our image down below, notice on the far left here, we have the isoprene unit from our previous lesson video and we know already that if we take multiple of these isoprene units and link them together, we can start to build our isoprenoids like these terpenes that we see here on the top half of our box. And so notice that we're showing you 3 different terpenes and the first one here is citral, this one here is batrapenal, and this one over here is called squalene, and this is a very important or key terpene that we'll talk more about later in our course. But one thing to note about all of these terpenes is that they're all relatively simple and linear isoprenoids. So, you can see that they have this linear structure and even squalene, if you look at it really closely, you'll notice that it truly does not have any cyclic structures in it. It has one end separate from the other end.

And so the terpenoids, on the other hand, are sometimes confused with terpenes, but the terpenoids are more complex isoprenoids. And they're typically derived from extensively modifying the terpenes. And so they have typically additional functional groups and they also tend to be cyclic compounds as well, and so if we take a look at the bottom half of our image, notice we're showing you 2 different terpenoids. We're showing you limonene here, which is commonly found in lemons and in your lemonade. And what you'll notice is that it does have a cyclic structure, but you can still see that it has these isoprene units inside ubiquinone, which is a terpenoid that's found in the mitochondria, and we'll talk more about this one much later in our course. But again, notice that this terpenoid has a cyclic structure and it also has these additional functional groups branching off, but you can still tell that there are these isoprene units embedded inside of them.

Now, if you're looking to determine the number of isoprene units within a terpene or terpenoid. Generally, in simple terpenes and terpenoids, the best indicator of the number of isoprene units is actually the number of methyl group branch points. And so, what I mean by that is where the methyl groups are actually branching off of, and so if we take a look at citral for instance, what you'll notice is that we've got a methyl group right here and a methyl group right here. And so the branch points of these methyl groups would actually be this carbon right here because that's what the methyl group is branching off of and this carbon right here because that's what this methyl group is branching off of. And so by counting the number of branch points, you can reveal the number of isoprene units. And so here, because there are 2 methyl group branch points that mean there are 2 isoprene units. Again, we have them highlighted here. Now notice that counting the number of double bonds is not always going to be the best indicator of the number of isoprene units because if we were to count the number of double bonds here, we would count that there are 3 double bonds. So counting the number of double bonds is not always the best indicator. The best indicator again to reveal the number of isoprene units is the number of methyl group branch points. And so, we'll be able to get some practice applying this idea here in our next video. So, I'll see you guys there.

How many isoprene units are present in the terpene molecule shown below?

A) 2.

B) 3.

C) 1.

D) 8.

E) 5.

F) 6.

• A. 2
• B. 3
• C. 1
• D. 8
• E. 5
• F. 6

Here’s what students ask on this topic:

What are isoprenoids and how are they classified?

Isoprenoids are a class of lipids formed from isoprene units, specifically 2-methyl-1,3-butadiene, a 5-carbon molecule. They are categorized into three major classes: terpenes and terpenoids, steroids, and lipid vitamins. Terpenes are linear isoprenoids, while terpenoids are more complex, often cyclic, and modified versions of terpenes. Steroids are another class of isoprenoids with a characteristic four-ring structure. Lipid vitamins, such as vitamins A, D, E, and K, are essential for various biological functions. Understanding these classifications is crucial for studying lipid functions and interactions in biological systems.

What is the difference between terpenes and terpenoids?

Terpenes are simple linear isoprenoids that are directly derived from isoprene units. They have a straightforward structure without cyclic components. Examples include citral and squalene. Terpenoids, on the other hand, are more complex isoprenoids that are typically derived from extensively modifying terpenes. They often contain additional functional groups and tend to be cyclic compounds. Examples of terpenoids include limonene and ubiquinone. The key difference lies in the complexity and presence of cyclic structures and functional groups in terpenoids.

How can you determine the number of isoprene units in a terpene or terpenoid?

The number of isoprene units in a terpene or terpenoid can be determined by counting the methyl group branch points. Each isoprene unit typically contributes a methyl group branch point. For example, in citral, there are two methyl group branch points, indicating two isoprene units. Counting double bonds is not a reliable method, as the number of double bonds does not always correlate with the number of isoprene units. Therefore, focusing on the methyl group branch points provides a more accurate count of isoprene units.

What are some examples of terpenes and their significance?

Examples of terpenes include citral, batrapenal, and squalene. Citral is commonly found in the essential oils of plants like lemongrass and is used in flavorings and perfumes. Batrapenal is another terpene with various applications in natural products. Squalene is a key terpene that serves as a precursor in the biosynthesis of steroids and other important biomolecules. These terpenes play significant roles in biological processes and have various industrial and pharmaceutical applications.

What are lipid vitamins and why are they important?

Lipid vitamins are a class of isoprenoids that include vitamins A, D, E, and K. These vitamins are essential for various biological functions. Vitamin A is crucial for vision and immune function. Vitamin D is important for calcium homeostasis and bone health. Vitamin E acts as an antioxidant, protecting cells from oxidative damage. Vitamin K is essential for blood clotting and bone metabolism. Deficiencies in these vitamins can lead to serious health issues, highlighting their importance in maintaining overall health.